The newly introduced option /tls-seclevel can be used to set the tls
security level on systems with openssl >= 1.1.0 or libressl.
As default level 1 is used as higher levels might prohibit connections
to older systems.
The async transport option is broken by design.
If used the main loop is called from the transport thread and the
main thread of the application.
Unless the transport layer is refactored to just work on queues
(input and output) this option will never work, therefore remove it.
Since redirection sometimes happens with internal DNS names that
are resolved different by outside DNS it must be possible to override
the preferred redirection hint.
Move the cmd struct to a extra header file. This allows it to only
include the header file in generate_argument_docbook.c and therefore
remove a linker dependencies.
